The present invention relates to an emergency capacitive energy source and circuit for fractional horsepower motors used as damper motors or as actuator motors.
Electric or electronic damper motors are utilized to open and close fresh air dampers, supply air dampers, smoke control dampers, return air dampers, relief dampers, fan vortex dampers, exhaust air dampers and fire dampers. These dampers are utilized to control the flow of air through air ducts. Other types of dampers are categorized as variable air volume terminal unit dampers, constant air volume terminal unit dampers, two position terminal unit dampers, fume hood supply and exhaust dampers and clean room supply and exhaust dampers. Again, these dampers are used to open and close vents in air ducts. Typically, the damper includes a motor which rotates a drive mechanism to open, close or position the air vents to certain locations thereby controlling the air flow through the duct work. Sometimes, the rotative movement of the motor is converted into linear movement thereby providing a linear damper actuator.
Valve actuators are generally classified as rotary valve actuators or linear push-pull valve actuators. Several types of valves can be controlled by such valve actuators. For example, two-way ball valves, three-way ball valves, two-way globe valves, three-way globe valves, two-way plug valves, three-way plug valves, butterfly valves, rotary delta P valves and shoe valves. Essentially, valve actuators convert a control signal into a valve drive signal which affects a motor in the actuator thereby mechanically changing the mechanical position of the valve stem control.
In many systems, it is commonplace to include a fail safe sub-system which closes or opens the damper or the valve in the event power is cut to the damper or valve actuator circuit or motor. For example, with respect to air dampers, it is a relatively common requirement that such air dampers be equipped with a fail safe system whereby, in the event that power is cut to the damper, the air vents are moved to a closed position to eliminate or reduce the probability that fire may spread within the building due to the open or partially open air ducts. In the past, these fail safe systems have included mechanical springs which automatically close the air vents or an independent hydraulic system which automatically close the air vents if power is cut to the motor controlling the air damper actuator. Since these fail safe systems must remain operable for a considerable length of time (2-10 years), it is critical that the fail safe system operates properly in the event that power to the damper actuator is cut off. Mechanical and hydraulic fail safe systems are subject to wear and tear and deterioration due to the somewhat continually opening and closing action of the air vents in the damper itself. If the dampers remain in an open or a closed position for a considerable period of time, the springs in a mechanical actuator may lose their retractive or compressive force or become mechanically damaged due to environmental conditions. Hydraulic fail safe systems are subject to leakage and corrosion due to environmental conditions.
It is sometimes necessary to include fail safe systems in valve actuators. For example, if the hydronic system is carrying hot or chilled water under system pressure, it may be necessary to include a fail safe system in the valve actuator. The valve actuator controls the flow of the water through the valve and through the hydronic system. In the event the control or drive signal applied to the valve actuator is cut off for any reason, the fail safe system would open or close the valve as required by design specifications. For hydronic systems, a fail safe "close" or "open" position may be required by the design specifications. Again, mechanical or hydraulic fail safe systems have been developed which automatically close the valve actuator and hence the valve if the drive signal for the valve actuator is cut off for any reason. Mechanical and hydraulic fail safe systems are subject to the same defects as specified above with respect to air dampers.
Air dampers and valve actuator motors are normally fractional horsepower AC or DC drive motors. These motors are sometimes called low output motors rather than fractional horsepower motors. A typical rating for these motors is up to 10 ounce inches of torque at maximum efficiency. Typical power consumption in the stall mode is up to 200 milliamps.
In addition, air damper actuators and valve actuators are normally relatively small components. A typical air damper actuator is sized about 6".times.6".times.10", not including its actuator arm, whether that arm is a linear actuator or a rotatable actuator. Valve actuators are similarly sized.
The control signals or drive signals customarily utilized in these air handling systems or hydronic systems are AC or DC control and drive signals. Accordingly, electronic or electric circuitry is associated with the air damper actuators and valve actuators which process analog and digital control signals. In some cases, the signal utilized to control the valve or the air damper is the same signal that is utilized to drive the actuator. For example, if a damper actuator was to be moved in a counterclockwise direction, an AC signal would be applied to the counterclockwise drive control line (CCWDRV). At another time, a clockwise drive power control signal (CWDRV) would be applied to the actuator. Accordingly, air damper actuators and valve actuators are relatively simple devices that are utilized at multiple locations in any given air handling system or hydronic system.